The present invention relates generally to cooktop ranges, and more particularly, to radiant electric heating units and control systems for cooktop ranges having the capability of detecting the presence of a cooking pan or utensil and methods of operating the same.
Several conventional cooktop ranges have a smooth glass-ceramic cooking surface. Mounted below the glass-ceramic cooking surface is one or more radiant electric heating units comprising typically of a coiled heater element. Power is supplied to the coiled heater element to heat a cooking pan or utensil placed on the glass-ceramic cooking surface. The glass-ceramic cooking surface is easier to clean than other types of cooktop ranges such as a gas range or a range that requires the pan to be placed directly on top of the heater element.
It has been known to detect the presence of a cooking pan or utensil on a cooktop range by using devices such as a weight sensor, a reed switch, or an optical sensor. These systems require extra components that may be subject to failure due to the high temperature environment of the heating unit.
Other previous attempts at pan detection involve placing coils around the outside of the heating element, embedding wires in the glass-ceramic cooking surface, or bonding wires to the bottom surface of the glass-ceramic cooking surface. More recently, there have been systems that deposit a gold foil pattern on the bottom surface of the glass-ceramic cooking surface. A current is sent through the wire or foil and any changes in the inductance is used by the control system of the cooktop to determine if a pan is present or absent. Each of these techniques requires expensive processing steps and requires materials that are capable of withstanding the high temperature environment. Moreover, replacement and maintenance of these systems may be difficult if the wire or foil fails.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
To that end, the present invention includes a control system for a heating unit in a cooktop that is capable of detecting the presence (or absence) of a cooking pan or utensil. The heating unit has a spirally wound ribbon heater element and may be mounted below a glass-ceramic cooking surface. The control system includes a pan detection unit electrically connected to the heater element. The pan detection unit generates a high frequency signal through the heater element to determine whether a pan is present on the cooktop. The pan detection unit may have an oscillation circuit to generate the high frequency signal through the heater element.
The control system may further include an electronic control unit that is electrically connected to the pan detection unit. The electronic control unit is capable of generating a signal to the pan detection unit to enable the pan detection unit to generate the high frequency signal through the heater element. In response, the pan detection unit is capable of sending a response signal to the electronic control unit that may reflect at least a portion of the reactance of the heater element. The electronic control unit may use this information to determine whether a pan is present. The control system may also include a user interface that is electrically connected to the electronic control unit.
The control system may further include at least one switch device. The at least one switch device is connected between the heater element and a power source. In one embodiment, the at least one switch device is opened when the pan detection unit generates the high frequency signal through the heater element.
In another embodiment, the present invention includes a control system for a heating unit in a cooktop that includes a pan detection unit, and at least one switch device. The heating unit has a heater element with a first terminal end and a second terminal end. The pan detection unit is electrically connected to the first and second terminal ends of the heater element. The pan detection unit is capable of generating a high frequency signal through the heater element to determine whether a pan is present on the cooktop. The at least one switch device is electrically connected between the heater element and a power source. The at least one switch device is opened to remove the power source from the heater element when the pan detection unit generates the high frequency signal through the heater element.
In a further embodiment, the present invention includes a control system for a heating unit with dual heater elements in a cooktop. In particular, the heating unit has an inner heater element and an outer heater element. The inner heater is spirally wound within the outer heater element. The control system includes a pan detection unit, a first switch device, and a second switch device. The pan detection unit is electrically connected to the inner and outer heater elements. The pan detection unit is capable of generating a high frequency signal through the inner heater element to determine whether a pan is present on the cooktop. The pan detection unit is also capable of generating a high frequency signal through the outer heater element to determine the size of the pan on the cooktop. The first switch device is electrically connected between the inner heater element and a power source. The first switch device is opened to remove the power source from the inner heater element when the pan detection unit generates the high frequency signal through the inner heater element in determining whether a pan is present on the cooktop. The second switch device is electrically connected between the outer heater element and the power source. The second switch device is opened to remove the power source from the outer heater element when the pan detection unit generates the high frequency signal through the outer heater in determining the size of the pan on the cooktop.
A further embodiment of the present invention includes a method of operating a heating unit for a cooktop with a control system that is capable of detecting whether a pan is present on the cooktop. The heating unit has a heater element and may be mounted below a glass-ceramic cooking surface. The method includes the steps of: receiving a setting from a user of the cooktop; generating a high frequency signal through the heater element; determining whether the pan is present on the cooktop from the generation of the high frequency signal through the heater element; isolating power to the heater element if it is determined that the pan is not present on the cooktop; providing power to the heater element if it is determined that the pan is present on the cooktop; determining whether the pan has been removed from the cooktop after power has been provided to the heater element; isolating power to the heater element if it is determined that the pan has been removed from the cooktop; and providing power to the heater element if it is determined that the pan has not been removed from the cooktop.
The step of generating the high frequency signal through the heater element may be performed by a pan detection unit having an oscillation circuit. The step of determining whether the pan is present on the cooktop may be performed by an electronic control unit that is electrically connected to the pan detection unit. The step of determining whether the pan has been removed from the cooktop may be performed by an electronic control unit that is electrically connected to the pan detection unit.
The above summary of the present invention is not intended to represent each embodiment, or every aspect of the present invention. This is the purpose of the figures and detailed description that follows.